1. Field of the Invention
The present invention relates to a pressure container manufacturing method and particularly, to a manufacturing method of a pressure container which is reinforced by covering a liner with a fiber reinforced composite material.
2. Description of Related Art
Currently, a pressure container for storing and transporting compressed gas such as CNG (Compressed Natural Gas), CHG (Compressed Hydrogen Gas) or the like, or low temperature gas has been in practical use. Earlier, a pressure container made of metal which has a high strength and is excellent in gas barrier property has been mainstream, however due to its heavy weight, there is a difficulty in applying it to a fuel tank of an automobile or a space plane in which weight saving is required. Therefore, recently, there has been proposed a relatively light weight FRP (Fiber Reinforced Plastics) wrapped pressure container which is made by forming an FRP layer on the outer periphery of a hollow cylindrical liner.
There is a FW (Filament Winding) method as a method to form the FRP layer on the outer periphery of the hollow cylindrical liner. The FW method is a method in which fiber bundles are impregnated with resin beforehand to prepare a tow-shaped prepreg and an FRP layer is formed by winding the tow-shaped prepreg on the liner. Applying the FW method is successful in obtaining an FRP wrapped pressure container which is relatively light in weight and has high strength. However, applying the FW method would raise a problem of requiring a long period of time to wind the tow-shaped prepreg on the liner.
To solve this problem, recently, there has been proposed a braiding method in which a braider is used to form a body on the outer periphery of the liner by braiding a plurality of fiber bundles, and the body is impregnated with resin to be cured to form the FRB layer (for example, refer to JP-Tokukaihei-11-58540A (Page 3, FIG. 4) or JP-Tokukaihei-07-256771A (Page 2, FIG. 2)). Applying the braiding method is successful in shortening the manufacturing time and reducing the manufacturing cost of the pressure container compared with the case of applying the FW method.
However, in the conventional braiding method, the body is formed on the periphery of the liner by supplying a fiber bundle from a plurality of bobbins of a braider which is disposed in a circumferential direction of the liner while moving the liner in an axial direction.
Conventionally, when forming a body on the periphery of the liner in this way, the movement of the liner is stopped when the forming position of the body reaches the root portion of the mouth piece of the liner. After the fiber bundles are cut off, the formation of the body is continued while the liner is moved in a direction opposite to the axial direction. Or alternatively when the forming position of the body reaches the root portion of the mouth piece of the liner, the liner is moved immediately in a direction opposite to the axial direction. After the fiber bundles are crooked greatly so as to be folded back, the formation of the body is continued.
In other words, in the conventional braiding method, when reversing the direction of the movement of the liner, the fiber bundles are cut off or alternatively the fiber bundles are crooked greatly so as to be folded back. For this reason, the FRP layer formed by using the conventional braiding method is lower in strength than the FRP layer formed by using the FW method.